Machine and method for wrapping products

ABSTRACT

A machine ( 1 ) and method for wrapping products ( 2 ), whereby a product ( 2 ) is applied with a respective sheet ( 3 ) of wrapping material, is fed by a wrapping conveyor ( 4 ) along a first path (P 1 ) to fold the sheet ( 3 ) of wrapping material about the product ( 2 ) to form a tubular wrapping ( 7 ), and is then fed by the wrapping conveyor ( 4 ) along a second path (P 2 ) to stabilize, by sealing, the tubular wrapping ( 7 ); a sealing element ( 11 ) being fed, by a further conveyor ( 12 ) and in time with the product, along a third path (P 4 ) parallel to the second path (P 2 ), so as to be applied to the second path (P 2 ), so as to be applied to the tubular wrapping ( 7 ) and seal two superimposed portions ( 8 ) of the tubular wrapping ( 7 ).

TECHNICAL FIELD

[0001] The present invention relates to a machine for wrapping products.

[0002] More specifically, the present invention relates to a continuous cellophaning machine for wrapping a packet of cigarettes in a respective sheet of transparent heat-seal material, to which the following description refers purely by way of example.

BACKGROUND ART

[0003] Currently marketed continuous cellophaning machines, for example of the type disclosed by EP-972704-A1, normally comprise a wrapping wheel having a number of seats, in each of which a respective packet of cigarettes is applied with a respective sheet of wrapping material, which is subsequently folded about the packet to form a tubular wrapping which is subsequently stabilized by heat sealing. To heat seal the tubular wrapping, it has been proposed to provide each seat on the wrapping wheel with a respective sealing head fitted to the wrapping wheel and movable between a rest position and a work position in which the sealing head contacts the respective tubular wrapping.

[0004] Wrapping wheels of the type described above are relatively complex, expensive and heavy, on account of the larger number of sealing heads and respective actuating devices housed on the wheel.

[0005] To overcome the above drawback, it has been proposed to perform the heat-seal operation along a sealing conveyor downstream from the wrapping wheel. Such a solution, however, while simplifying the wrapping wheel, increases the size and cost of the cellophaning machine as a whole. Moreover, transferring the unstabilized tubular wrappings from the wrapping wheel to the sealing conveyor is complicated by the tendency of the folded sheet of wrapping material to spring back to its original configuration.

DISCLOSURE OF INVENTION

[0006] It is an object of the present invention to provide a machine for wrapping products, designed to eliminate the aforementioned drawbacks, and which at the same time is cheap and easy to produce.

[0007] According to the present invention, there is provided a machine as recited in Claim 1.

[0008] The present invention also relates to a method of wrapping products.

[0009] According to the present invention, there is provided a method as recited in Claim 25.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

[0011]FIG. 1 shows a schematic elevation of a preferred embodiment of the machine according to the present invention;

[0012]FIG. 2 shows a larger-scale elevation of a detail in FIG. 1;

[0013]FIG. 3 shows a section along line III-III in FIG. 2;

[0014]FIG. 4 shows a larger-scale elevation of a further detail of the FIG. 1 machine;

[0015]FIG. 5 shows a larger-scale elevation of a variation of a detail in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Number 1 in FIG. 1 indicates as a whole a machine for wrapping packets 2 of cigarettes in respective sheets 3 of heat-seal wrapping material, in particular, sheets of polypropylene or similar. Machine 1 comprises a wrapping wheel 4, which rotates continuously about a respective horizontal axis 5 perpendicular to the FIG. 1 plane, and has a number of peripheral seats 6. Each seat 6 receives a respective packet 2 and a respective sheet 3 of wrapping material at an input station S1, and feeds respective packet 2 and respective sheet 3 of wrapping material along a wrapping path P1 and a subsequent stabilizing path P2 to an output station S2.

[0017] Along wrapping path P1, each sheet 3 of wrapping material is folded in known manner about respective packet 2 to form a tubular wrapping 7 by superimposing two end portions 8 of sheet 3 of wrapping material; along stabilizing path P2, each tubular wrapping 7 is stabilized by heat sealing the two end portions 8 to each other; and, once the sealing operations are completed, each wrapping 7 reaches output station S2 where it is expelled from respective seat 6 by a known unloading device not shown.

[0018] Machine 1 also comprises a sealing device 9, which in turn comprises a number of sealing members 10, each having a respective known sealing head 11, which is heated by means of a respective known electric resistor (not shown) and is applied to a respective tubular wrapping 7 for a given length of time to heat seal respective superimposed end portions 8. Sealing device 9 also comprises a belt conveyor 12, which has an endless flexible belt 13 supporting sealing heads 11 on its outer face 14. In a preferred embodiment, the number of sealing members 10 equals the number of peripheral seats 6, so that each peripheral seat 6 operates at all times with the same sealing member 10, thus simplifying adjustment and set-up of machine 1.

[0019] Each sealing member 10 is fed by belt 13 in time with a respective wrapping 7 and along a path P3 parallel to path P2, so that each sealing head 11 is applied to respective tubular wrapping 7 for a given length of time and so heat seals tubular wrapping 7. More specifically, path P3 forms a portion of an endless path P4, along which sealing heads 11 are fed cyclically by the continuous movement of belt 13.

[0020] As shown clearly in FIG. 1, paths P1, P2, P3 are substantially arcs of a circle with a common center at axis 5.

[0021] Conveyor 12 also comprises a guide device 15 for feeding belt 13 along endless path P4 and, in particular, along curved portion P3. Guide device 15 comprises three end pulleys 16, 17, 18 having respective axes of rotation parallel to axis 5 and about which belt 13 is wound. Pulleys 16 and 17 are located at opposite ends of path P3, while pulley 18 is located between pulleys 16 and 17 to define, with pulleys 16 and 17, the vertices of an isosceles triangle. In a preferred embodiment, pulley 17 is powered, and pulleys 16 and 18 are idle. The rotation speed of pulley 17 is such that the peripheral speed of sealing heads 11 along path P3 equals the peripheral speed of seats 6 along path P2.

[0022] Guide device 15 also comprises a contoured track 19 of the same shape as path P4; and a connecting device 20 for connecting belt 13 to track 19. In an alternative embodiment not shown, track 19 only extends along path P3. Contoured track 19 is defined by two identical facing grooves 21 formed in two parallel flat plates 22, which are perpendicular to axis 5 and located on opposite sides of belt 13.

[0023] Connecting device 20 comprises a number of carriages 23, each of which is supported by a respective appendix 24 fixed to the inner face 25 of belt 13, engages both grooves 21, and comprises a shaft 26 integral with respective appendix 24 and supporting, at opposite ends, two idle wheels 27, each rolling along respective groove 21.

[0024] Each flat plate 22 is substantially rectangular and has a semicircular recess at and for avoiding interference with wrapping wheel 4.

[0025] In the FIG. 5 embodiment, guide device 15 only comprises end pulleys 16 and 17 having respective axes of rotation parallel to axis 5, and about which belt 13 is wound. Each sealing head 11 is fitted to a respective substantially Z-shaped frame 28 comprising a central plate 29, which, at one end, has a lateral appendix 30 facing belt 13 and connected to belt 13 by a transverse hinge 31 parallel to the axes of pulleys 16 and 17, and, at the other end, has a lateral appendix 32 facing outwards and supporting respective sealing head 11 by a hinge 33 parallel to hinge 31. At lateral appendix 32, supporting frame 28 is connected to belt 13 by a connecting rod 34 enabling frame 28 to adapt to the varying curvature of belt 13.

[0026] Each sealing head 11 substantially faces plate 29 of relative frame 28, and oscillates about relative hinge 33 between a work position (FIG. 5) in which sealing head 11 contacts a respective wrapping 7 traveling along path P2, and a rest position in which sealing head 11 does not contact a respective wrapping 7 traveling along path P2. The angular position of ach sealing head 11 about relative hinge 33 is controlled, on one side, by an elastic thrust system 35 interposed between sealing head 11 and relative frame 28 and for maintaining sealing head 11 in said work position, and, on the other side, by a return device 36 for moving sealing head 11 towards relative plate 29 and into said rest position.

[0027] Return device 36 comprises an armature 37 of ferromagnetic material, which is hinged at one end to relative sealing head 11 and engages in sliding manner two through holes 38 and 39 formed through relative plate 29 and belt 13 respectively. The portion of each armature 37 projecting inwards of belt 13 interferes, as armature 37 travels along path P3, with a magnetic field generated by a series of electromagnets 40 carried by plates 22 and which provide for moving sealing heads 22 away from wrappings 7.

[0028] In actual use, the length of time each sealing head 11 is applied to respective wrapping 7 is maintained constant alongside changes in the traveling speed of wrapping 7 along path P2, i.e. in the rotation speed of wrapping wheel 4, by varying the actual length of path P3 by means of electromagnets 40, which provide for adjusting the length of path P3 along which sealing heads 11 are applied to respective wrappings 7.

[0029] Sealing heads 11 are made of material of relatively low thermal inertia and relatively high electric resistance, and are connected to one another in series by electric cables (not shown) to form a single endless turn 41, along which flows an alternating electric current generated by induction by a variable magnetic field in turn generated by a known generating device 42 (shown schematically) connected magnetically to turn 41. Adjusting the intensity and/or frequency with which the variable magnetic field is varied regulates the intensity of the current circulating in turn 41, and therefore the working temperature of sealing heads 11.

[0030] In a variation not shown, the functions of elastic system 35 and return device 36 are inverted, i.e. elastic system 35 keeps sealing head 11 in said rest position, and return device 36 moves head 11 into said work position.

[0031] In this case, too, the actual length of path P3 is adjusted by means of electromagnets 40, which, in this case, however, exert a force of repulsion to restore sealing heads 11 from the rest to the work position.

[0032] Finally, in a further variation not shown, return device 36 is dispensed with, and the actual length of path P3 is adjusted, for each sealing head 11, by short-circuiting the ends of head 11 in controlled manner.

[0033] In this case, however, the length of time each sealing head 11 is actively applied to respective wrapping 7 is maintained constant, alongside variations in the rotation speed of wrapping wheel 4, by deactivating sealing head 11 as opposed to moving it away from relative wrapping 7. 

1) A machine (1) for wrapping products (2) the machine (1) comprising a first conveyor (4) for continuously feeding a the product (2), applied with a respective sheet (3) of heat-sealable wrapping material, along a first path (P1) to fold the sheet (3) of heat-sealable wrapping material about the product (2) to form a wrapping (7), and for feeding the product (2) along a second path (P2) subsequent to the first path (P1); and heat sealing means (10) which are applied to the wrapping (7) along the second path (P2) to stabilize, by heat sealing, the wrapping (7); the machine (1) being characterized by comprising a second conveyor (12) independent from the first conveyor (4) and for feeding the heat sealing means (10) in time with the product (2) and along a third path (P3) parallel to the second path (P2). 2) A machine (1) as claimed in claim 1, wherein the first conveyor (4) comprises a number of peripheral seats (6), each for receiving a relative the product (2) together with a respective sheet (3) of wrapping material; each the seat (6) being associated with a respective the heat sealing means (10). 3) A machine (1) as claimed in claim 1 or 2, wherein the first, the second and the third path (P1, P2, P3) are curved paths. 4) A machine (1) as claimed in one of claims 1, 2 and 3, wherein the first conveyor (4) is a wrapping wheel (4), and the first, the second and the third path (P1, P2, P3) are defined by coaxial arcs of a circle. 5) A machine (1) as claimed in one of claims 1 to 4, wherein the wrapping (7) is a tubular wrapping. 6) A machine (1) as claimed in one of claims 1 to 5, wherein the heat sealing means (10) comprise a plurality of heat sealing heads (11). 7) A machine (1) as claimed in one of claims 1 to 6, wherein the second conveyor (12) is a belt conveyor (12) and comprises an endless belt (13) supporting the heat sealing means (10); the second conveyor (12) comprising guide means (15) for feeding the belt (13) along the third path (P3). 8) A machine (1) as claimed in claim 7, wherein the guide means (15) comprise a track (19) of the same shape as the third path (P3); and connecting means (20) for connecting the belt (13) to the track (19). 9) A machine (1) as claimed in claim 8, wherein the track (19) extends along the whole path (P4) of the belt (13). 10) A machine (1) as claimed in claim 8 or 9, wherein the track (19) is defined by two grooves (21) formed in two flat plates (22) located on opposite sides of the belt (13). 11) A machine (1) as claimed in claim 10, wherein the connecting means (20) comprise a number of carriages (23) running inside the groves (21) and integral with the belt (13). 12) A machine (1) as claimed in claim 11, wherein each the carriage (23) comprises a shaft (26) integral with the belt (13); and two end wheels (27) fitted idly to the shaft (26). 13) A machine (1) as claimed in claim 12, wherein the belt (13) has an outer face (14) to which the heat sealing means (10) are fixed; and an inner face (25) from which project appendixes (24) supporting the shafts (26). 14) A machine (1) as claimed in one of claims 6 to 13, wherein each the heat sealing head (11) comprises a heating resistor of relatively low thermal inertia and relatively high electric resistance. 15) A machine (1) as claimed in claim 14, wherein the heating resistors are connected in series to form a single endless turn (41); means (42) for generating a time-variable magnetic field being connected magnetically to the turn (41). 16) A machine (1) as claimed in claim 14 or 15, wherein each the heating resistor is short-circuitable to adjust the actual length of the third path (P3). 17) A machine (1) as claimed in one of claims 6 to 16, wherein each the heat sealing head (11) is connected to the belt (13) by a respective frame (28) hinged to the belt (13) at two points. 18) A machine (1) as claimed in claim 17, wherein the frame (28) has a first end hinged directly to the belt (13), and a second end connected to the belt (13) via the interposition of a connecting rod (34). 19) A machine (1) as claimed in claim 17 or 18, wherein each the heat sealing head (11) is connected to the respective the frame (28) so as to move, with respect to the frame (28), from a work position to a rest position in opposition to elastic means (35). 20) A machine (1) as claimed in claim 19, wherein each the heat sealing head (11) is hinged to the respective the frame (28); return means (31) being provided to swing the heat sealing head (11) from a work position to a rest position in opposition to the elastic means (35). 21) A machine (1) as claimed in claim 20, wherein each the return means (31) comprises an armature (37) made of ferromagnetic material, connected to the relative the heat sealing head (11), and movable with the heat sealing head (11) along the third path (P3); and electromagnets (40) distributed along the third path (P3). 22) A machine (1) as claimed in claim 17 or 18, wherein each the heat sealing head (11) is connected to the respective the frame (28) so as to move, with respect to the frame (28), from a rest position to a work position in opposition to elastic means (35). 23) A machine (1) as claimed in claim 22, wherein each the heat sealing head (11) is hinged to the respective the frame (28); return means (31) being provided to swing the heat sealing head (11) from a rest position to a work position in opposition to the elastic means (35). 24) A method of wrapping a product (2); the method comprising applying the product (2) with a respective sheet (3) of wrapping material; feeding the product (2) and the sheet (3) of wrapping material along a first path (P1) by means of a wrapping conveyor (4) to fold the sheet (3) of wrapping material about the product (2) to form a wrapping (7); and feeding the wrapping (7), by means of the wrapping conveyor (4), along a second path (P2) to stabilize the wrapping (7); the method being characterized by feeding heat heat sealing means (10), in time with the product, along a third path (P3) parallel to the second path (P2) by means of a second conveyor (12) independent from the first conveyor (4), so as to apply the heat sealing means (10) to the wrapping (7) and stabilize, by heat sealing, the wrapping (7). 25) A method as claimed in claim 24, wherein the length of time the heat sealing means (10) are applied to the wrapping (7) is maintained constant, alongside variations in the traveling speed of the wrapping (7) along the second path (P2), by varying the actual length of the third path (P3). 